Hi Alizah,
In another post (here:
https://gmatclub.com/forum/how-to-impro ... l#p2113873), you stated that you wanted to raise a 510 (which you scored on the Official GMAT) to 680+. That type of improvement will take a considerable amount of time and effort. It's also important to remember that a CAT is really a 'measuring device' - when used correctly, it will give you a realistic score and help define your strengths and weaknesses, but it will NOT help you to fix any of those weaknesses. To raise your scores, you have to learn the necessary Tactics and put in the proper practice and repetitions. The CAT will show you whether your studies are helping you to improve or not. As such, you really shouldn't take more than 1 FULL CAT per week (and at this point, you might only take one every 2 weeks until you get a bit closer to Test Day).
Before you purchase any additional CATs, it would be a good idea if you provided a bit more information on how you've studied so far - so you might want to answer the questions that were asked in that other post.
GMAT assassins aren't born, they're made,
Rich